Scala 如何知道“def foo"和“def foo"之间的区别?和“def foo()"? [英] How does Scala know the difference between "def foo" and "def foo()"?

问题描述

我知道scala中空参数和无参数方法的用法区别，我的问题与生成的类文件有关.当我在 javap 中查看这两个类时，它们看起来完全一样:

I know about the usage difference between empty-parameter and parameterless methods in scala, and my question pertains to the class file generated. When I look at these two classes in javap, they look exactly the same:

class Foo {
  def bar() = 123;
}


class Foo {
  def bar = 123;
}

但是当我在 scalap 中查看它们时，它们准确地反映了参数列表.scalac 在类文件中的哪个位置明确了这种区别?

But when I look at them in scalap, they accurately reflect the parameter lists. Where in the class file is scalac making this distinction known?

推荐答案

在 .class 文件中，有一个名为 ScalaSig 的类文件属性，其中包含 Scala 所需的所有额外信息.它不是人类真正可读的，但它就在那里:

In the .class file, there is a class file attribute called ScalaSig, which contains all of the extra information needed by Scala. It's not really readable by humans, but it is there:

$ javap -verbose Foo.class
const #195 = Asciz      ScalaSig;
const #196 = Asciz      Lscala/reflect/ScalaSignature;;
const #197 = Asciz      bytes;
const #198 = Asciz      ^F^A!3A!^A^B^A^S\t\tb)^[7f^Y^Vtw\r^^5DQ^V^\7.^Z:^K^E\r!^
Q^A^B4jY^VT!!^B^D^B^UM^\^W\r\1tifdWMC^A^H^....

另见 Scala 签名是如何存储的? 和 scala.reflect.ScalaSignature，这是'非常有趣:-)

See also How is the Scala signature stored? and scala.reflect.ScalaSignature, which isn't very interesting :-)

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